6  THE EVOLUTION OF MAN. 



history of man. The most important source from which 

 the science derives its material, is Ontogeny, or the history 

 of germs, in other words, of the evolution of the individual, 

 Palgeontology, or the science of petrifactions, and, in a yet 

 greater degree. Comparative Anatomy, also aflord most im- 

 portant aid to Phylogeny. , 



These two divisions of our science. Ontogeny, or the 

 history of the germ, Phylogeny, or the history of the 

 tribe, are most intimately connected, and the one cannot 

 be understood without the other. . The close intertwining 

 of both branches, the increased proportions which germ- 

 history and tribal history lend to each other, alone raise 

 Biogeny ^ (or the history of organic evolution, in the widest 

 sense) to the rank of a philosophic natural science. The 

 connection between the two is not external and superficial, 

 but deeply internal and causal. Our knowledge of this 

 connection has been but very recently obtained ; it is most 

 clearly and accurately expressed in the comprehensive state- 

 ment which I call ^'tke fundamental law of organic 

 evolution',' or more briefly, " the first principle of Biogeny " ' 



This fundamental law, to which we shall recur again 

 and again, and on the recognition of which depends the 

 thorough understanding of the history of evolution, is briefly 

 expressed in the proposition : that the History of the Germ 

 is an epitome of the History of the Descent ; or, in other 

 W()rds : that Ontogeny is a recapitulation of Phylogeny ; or, 

 somewhat more explicitly: that the series of forms through 

 which the Individual Organism passes during its progress from 

 the egg cell to its fully developed state, is a brief, compressed 

 reproduction of the long series of forms through which the 

 animal ancestors of that organism (or the ancestral forms 



